As Mary Petersen, I usually use elutriation for separating macro and
meiofauna from sediment. I put the sample or a fraction of it into a
decantation funnel connected by its narrow opening to a tap. The water
pass across the sample dragging the fauna, exits by the top of the funnel
and it is conducted to a sieve in which the animals and debris are retained.
If the sample is previously stained it is easy to see how the fauna leaves
the sediment, after a few minutes, all animals and debris have been
extracted while the sediment remains in the funnel. With the tap, you may
regulate the flow at each moment in order to optimise the extraction.
The problem arises when molluscs are present in the sample since they are
difficult to separate from sediment and it is necessary to extract them by
hand. However, Robinson, S.M.C. el al (1993) describes a technique to
separate molluscs:
Record 4 of 8 in ASFA 1988-1996
TI: An effective and safe method for sorting small molluscs from sediment
AU: Robinson,-S.M.C.; Chandler,-R.A.
SO: LIMNOL.-OCEANOGR. 1993 vol. 38, no. 5, pp. 1088-1091.
LA: English
AB: A method is presented which enables infaunal juvenile bivalves to be
separated from associated sediment with a combination of elutriation and
flotation techniques. Simple elutriation is used to remove less dense
organic detritus and a relatively new, nontoxic compound (sodium
polytungstate) is used to create a heavy liquid that sorts the bivalves from
sediment by relative density. The technique was applicable to 12 species of
molluscs of various sizes and was 98-100% effective in separating juvenile
Mya arenaria, ranging from 0.5 to 24 mm in shell length, from surrounding
sediment.
AN: 3006368
Román Porras
rporras at mail.ono.es
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